Mick Philpott and his wife, Mairead, speaking to the media following the fire at their home last year. Photograph: Rui Vieira/PA

A mother accused of killing her six children in a house fire has told a court it was possible that her husband got out of bed to start the blaze.

Mairead Philpott, 31 told jurors she did not know who had set the fire at her home because she was asleep when it started. During her second day of testimony at Nottingham crown court, she also denied "working together as a team" with her husband Mick, 56, to cover up their alleged involvement in the blaze.

The Philpotts and their friend Paul Mosley, 46, all deny the manslaughter of the six children who died in the fire in Derby.

Asked by prosecutor Richard Latham QC whether she was suggesting that her husband had got out of bed shortly before the fire in the early hours of 11 May last year, Mairead Philpott replied: "It's possible. I don't know because I was asleep."

Latham then asked: "Are you saying that there is a possibility that your husband set this fire behind your back literally?"

She replied: "I honestly don't know. I can't rule out anybody – I just don't know who set the fire."

Mrs Philpott insisted that covert recordings made of conversations after the fire in which she discussed "sticking with the story" were references to her having sex with Mosley.

Latham put it to her that they had been talking about the allegation that they were responsible for the fire.

But she told the jury that the phrase "sticking with the story" was a reference to not telling anyone about the sexual activity with Mosley.

"It was about the sex," she told the court. "I didn't want to be disgraced in the papers. My children had just died – I was more bothered about my children."

During Latham's cross-examination, she accepted that she had been a "fully functioning participant" in the conversations covertly recorded by the police following the fire.

But she denied that they showed "deviousness" on the part of her and her husband.

Responding to Latham's claim that she was not "hysterical" during a 999 call on the morning of the fire, she added: "I was panicking, I just wanted to get to my children – I didn't know what was happening."

Mrs Philpott said it was possible her husband could have stepped out of their bed without her knowledge after she turned off the television and went to sleep.

During detailed questioning about the covert police recordings, she said of her earlier evidence: "I said I didn't know if Mick is capable of doing it - I don't know if he has done it or not."

Mr Latham submitted that the evidence in the case meant the "scenario" in which Mick Philpott had committed arson alone could sensibly be ignored.

Accusing Mrs Philpott of lying, the prosecutor added: "Either you are both not guilty and it's a third party, or you knew perfectly well that he did it because you were part of it.

"The jury, being sensible about it, can really put on one side this idea that he did it behind your back."

Latham went on to question her about traces of petrol found on her leggings, a thong and a sink at the fire-hit house. He asked: "What was going on with Total petrol in that sink that night?"

Mrs Philpott, who claims to have found out that the house was on fire only after being woken by a smoke alarm, replied: "I don't know."

The Philpotts are accused of setting the fire at their home to frame Mr Philpott's former mistress, whom he was due to face in court later the same day to discuss custody of their children.

Mosley is alleged to have taken part in a "rehearsal" prior to the fire.

Jade Philpott, 10, John, nine, Jack, eight, Jesse, six, and Jayden, five, all died in the blaze. Duwayne, 13, died in Birmingham Children's Hospital days later.